1. Field of the Invention
The present invention refers to an improved filter assembly, particularly for electric cabinets.
2. Background Art
In the current art, in order to cool electric panels, air filtering systems are employed which are equipped with fans (of the axial, radial or the like type) adapted to force air through filter clothes adapted for filtering air.
In such known systems, the fan applied to the filter assembly must exceed the resistance to air crossing the filter, such resistance occurring with a load leakage, which increases the pressure that the fan must exceed with consequent decay of performance in terms of air flow-rate.
In particular, upon increasing the filter clogging, the further flow-rate decays cannot be computed by the user and often can drop (even quickly in case of very dirty atmospheres) under the minimum value, which guarantees an enough cooling of the device placed inside the electric cabinet.
A solution which has already been adopted in this case is providing a cabinet with a thermostat which is triggered upon reaching a limit temperature, but such thermostat will necessarily measure the temperature in a single spot, and with a reduce flow-rate a reduced internal venting (meant as air stirring inside the electric cabinet) is also associated, with consequent creation of dangerous and uncontrolled localised “hot spots”.
Moreover, should venting be completely absent, but the external temperature be low enough, the relevant thermostat would not intervene at all, while “hot spots” would be at their maximum level.
For an optimum monitoring of temperature and venting inside the cabinet, it would be ideal to be able to monitor different alarm parameters and create better venting conditions.
The affected parameters are:                air flow-rate towards cabinet interior;        temperature inside the cabinet;        fan failures.        
Fans of filters can be of the sucking or pressing type (namely can be both able to suck air inside the cabinet and able to pump out exhaust air) and it is extremely interesting that they operate indifferently along the two directions whichever type of sensor is used.
A further improvement with respect to the prior art would be to allow a higher venting inside the cabinet by short-circuiting permanently, or in case of need, part of the internal air.